As technology for inspecting a measurement object such as an integrated circuit, there is an optical probing technology for radiating light emitted from a light source to a measurement object and detecting measurement light (reflected light) from the measurement object by a light sensor to acquire a detection signal. In this optical probing technology, a method of disposing a magneto-optical (MO) crystal (e.g., see Patent Literature 1 and 2) facing an optical irradiation plane of a measurement object and acquiring a detection signal by detecting reflected light according to a magneto-optical effect of the MO crystal is known.